Various forms of encapsulating materials in glass articles have been known in the past such as shown by the ornamental glass bottle of U.S. Pat. No. 502,461 and the wired glass ribbon of U.S. Pat. No. 3,305,335. The ornamental glass bottle of the former patent has encapsulated particles formed in the bottom wall by initially pressing molten glass onto a layer of pulverized glass particles to form an amalgamation between the two in the form of a circular base. The base, after being rigidified, is inverted and placed on the bottom of a blow mold and a glass bottle is blown in the mold, which bottle covers the amalgamated particles of the base and encapsulates the particles between the pressed glass and the blown glass into the bottom of the blown bottle. In the latter patent, a wire web is encapsulated between two layers of molten glass as it passes between a pair of casting rollers to form a ribbon of wired glass.
In addition to full encapsulation of materials in glass articles as shown in said aforementioned patents, it is also been known to seal or secure articles in molten glass during a pressing operation, such as shown in U.S. Pat. Nos. 314,828 and 2,219,573 and as suggested on page 22 of THE GLASS INDUSTRY, April 1978. In U.S. Pat. No. 314,828, a charge of molten glass is deposited in a mold, and a plunger carrying a metallic shank descends into the molten glass for the purpose of pressing the molten glass into the shape of a glass knob and embedding one end of the shank therewithin. U.S. Pat. No. 2,219,573, on the other hand, discloses the formation of a glass panel having an integral metal frame by positioning the frame within a mold and pressing a gob of molten glass into contact therewith so as to embed an inner peripheral flange of such frame within the glass panel. Such patent also discloses the positionment of pins within a mold assembly so as to press form a gob thereabout and integrally seal the pins in the thus formed glass body. THE GLASS INDUSTRY article entitled "The Mechanical and Chemical Aspects of Glass Sealing--Part II" by Marcus T. Borom (pp.19-26) indicates on page 22 that from a manufacturing standpoint it is possible to form a glass-to-metal seal by embedding metal hardware in a mold, casting glass around it, and transforming the part to a glass-ceramic.
As can be seen from the foregoing prior art, a variety of reasons existed for the desirability of encapsulating or sealing different materials within glass articles. The present invention relates to the pressing of a thermally conducting insert within a pressed glass article, such as top of the stove cooking vessels, for the purpose of providing a more even distribution of heat over heat transmitting surfaces of such vessels, whether the heat be generated by conventional conduction means or by radiation, induction or microwave means. Accordingly, in view of the foregoing, U.S. Pat. No. 3,410,989 is of particular interest. As set forth in such patent, a glass or glass-ceramic article in the form of a cooking vessel has a recess of relatively large planar area formed in the bottom thereof with a graphite heat transfer member positioned in such recess, and a plate of the same material as the vessel overlies such member so as to seal the member within such recess with a high temperature cement. Although it appears that the vessel is initially formed with the recess therein or that it is subsequently machined in the bottom surface thereof such that an outer plate of the same material may be cemented therein with a snug fit, the patent further points out that the vessel could be press formed in a conventional manner and a graphite plate sealed to the bottom thereof by pressing a second gob of molten glass thereon. As envisioned by the patent, the article would initially be press formed from a gob of molten material in a manner known in the art, and then permitted to cool to a temperature below its softening point temperature. A graphite plate would then be positioned adjacent a bottom surface of the article and the article reheated to near its softening point temperature. Another gob of molten material would then be deposited upon the graphite plate and press formed to provide a covering plate for the graphite plate. The molten material of the covering plate would become fusion sealed with the material of the article to hermetically seal the graphite plate within the bottom of the article.
Both the cemented plate method and the second gob method of encapsulating the graphite plate as disclosed in the aforesaid patent, not only require costly and time consuming fabrication techniques, but also tend to trap air in the encapsulated cavity and do not necessarily lend themselves to the bonding of the encapsulated part to the pressed article should such be desired. Further, although not part of the prior art, the applicant is aware of other attempts to encapsulate silicon, graphite and the like in pressed articles wherein an insert was positioned between a first gob or patty and a second gob or patty, and then pressed into an article; and wherein a first gob was initially pressed, an insert placed thereon and a second gob pressed over the first, either with or without a delay between such pressings. However, hereagain, air had a tendency to become trapped about edge portions of the insert, producing defects in the glass article and preventing complete bonding of the insert to the gob material where desired. Further, since these approaches did not provide proper support for the insert, it had a tendency to shift location and/or crack upon pressing.
It thus has been an object of the present invention to provide method and apparatus for easily and economically encapsulating a thermally conductive insert within a pressed article as the article is being press formed from molten glass.